The invention relates to a device supporting a light-emitting diode (LED) for an automobile signalling or lighting system, comprising an insulating support, in particular made from plastics material, and means of connection to the electrodes of the light-emitting diode.
Use is already made, for signalling, of low-power light-emitting diodes. In order to obtain a sufficient light flux, for example of at least 30 lumens, and to fulfil a signalling function, several diodes are combined. The heat produced within each low-power diode is discharged in a satisfactory manner by the electrodes providing the electrical connection. Good heat dissipation is in fact necessary since the light efficiency of a light-emitting diode decreases if its junction temperature increases.
The progress made makes it possible now to obtain power light-emitting diodes whose light flux exceeds 30 lumens. The heat release by the power diode is great and cannot be discharged in a satisfactory manner by the electrodes. A power diode is thus generally provided with a base for establishing effective thermal contact with a heat dissipation means.
A single power light-emitting diode could fulfil an automobile signalling function, for example a stop light or side light, but its installation poses a problem, in particular with the heat dissipation.
In the electronics industry power light-emitting diodes are used. For mounting them use is generally made of a circuit known by the term xe2x80x9cMCPCBxe2x80x9d (Metal Core Printed Circuit Board), which corresponds to a solution resulting from techniques used in electronics. The circuit is rigid, and serves as a physical support, electrical conductor and heat dissipater.
Such a solution is too costly for the automobile sector and cannot be suitable. In addition, its compatibility with automobile signalling techniques is not satisfactory.
The aim of the invention is in particular to optimise the use of power light-emitting diodes for producing automobile signalling and lighting systems at a sufficiently low cost price to be acceptable. An optimisation of this type entails an effective extraction of the heat produced by the diode in order to optimise the performance with regard to the usable light flux.
According to the invention, a device supporting a power light-emitting diode for an automobile signalling or lighting system comprises an insulating support, in particular made from plastics material, and means of electrical connection to the diode electrodes, and is characterised by the fact that the electrical connection means comprise, on the insulating support, electrical connection lugs, the fact that the body of the light-emitting diode is fixed to an area of a heat-radiating element, the fact that this heat-radiating element is attached to the insulating support, and the fact that the electrodes of the diode are insulated from the heat-radiating element and electrically connected to the connection lugs of the insulating support.
The heat-radiating element preferably comprises, on its contour, at least one scallop in the direction of the light-emitting diode fixing area, at least one of the diode electrodes is disposed in a corresponding scallop in the radiating element, and the electrical connection means comprise, in the scallop or in each scallop, a tongue made from electrically conductive material whose edges are distant from those of the scallop and whose external radial end is situated in the vicinity of or beyond the external contour of the radiating element.
The invention makes it possible to provide, effectively, an automobile signalling function, for example a stop or side light, with a single power light-emitting diode.
The invention exploits a synergy between a purely electronic technique and a specific technique of the automobile signalling sector. The result is an optimisation of costs, the maintenance of compatibility with the methods used for conventional light sources, and the maintenance of basic qualities of signalling devices already existing.
The support device according to the invention constitutes a specialised terminal for a power light-emitting diode, making it possible to preserve the specificity of a terminal for a conventional lamp. The terminal forms an interface between an electronic board and the light-emitting diode via a connection system.
The power light-emitting diode can produce a light flux of at least 30 lumens, in particular at least 40 lumens.
The radiating element can be obtained from a sheet of metal which is a good conductor of heat and electricity, in particular a sheet of copper, with a relatively low thickness, for example less than 1 mm. The rigidity, when the device is mounted, is provided by the connection to the insulating support.
The fixing area for the base of the light-emitting diode preferably consists of the central area of the radiating element, which comprises two opposite scallops starting from its contour and directed towards the central area; each electrode of the diode is situated respectively in a scallop, and an electrically conductive tongue is situated in each scallop and is connected to the corresponding electrode, the edges of the tongue being distant from those of the scallop.
The tongue advantageously consists of a cut-out part of the sheet or plate forming a radiator, in correspondence with a scallop.
In such a support device, the thermal function of discharge of the heat by the radiating element is separate from the electrical conduction function provided by the tongues disposed in the scallops and electrically insulated from the radiator.
The edge of the tongue remote from the light-emitting diode can project beyond the contour of the radiating element in order to facilitate electrical connection.
The assembly of the radiating element and insulating support can be provided by cooperation of holes provided in the radiating element and pins, studs or rivets provided on the insulating support.
The diode electrodes can be spot welded, in particular by laser.
The invention also relates to a method of manufacturing a support device as defined above, this method being characterised by the fact that there are prepared separately an insulating support, in particular made from plastics material, provided with electrical connection lugs, and a radiating assembly comprising a power light-emitting diode, and that the radiator and insulating support are assembled mechanically whilst providing the electrical connection of the diode electrodes with the connecting lugs.
Advantageously, the radiating assembly is produced from a sheet or plate of metal which conducts heat and electricity, in particular copper, from which there are partially cut, on each side of a central area, tongues which remain temporarily connected by fasteners with a reduced cross-section, forming shunts, to the major part of the sheet or plate in order to ensure its coherence and mechanical holding; the light-emitting diode is positioned and fixed, in particular by adhesive bonding, to the central area of the radiating element; each diode electrode is welded with a respective tongue and the connecting shunts between tongues and radiating element are next broken so as to provide the electrical insulation of each tongue vis-à-vis the radiating element.
The connecting shunts between a tongue and the radiating element have sufficient cross-section to provide mechanical holding, but relatively small so as to limit the discharge of heat through the shunts when the electrodes are welded to the tongues.
With its two opposite scallops the radiating element has substantially an H shape with broad legs.
The invention consists, apart from the arrangements disclosed above, of a certain number of other arrangements which will be dealt with more explicitly below with regard to example embodiments described in detail with reference to the accompanying drawings, but which are in no way limiting.